Lagging audio playback in the VSE?
Try using the VSE proxy function, Blender will render lower resolution media for all strips that have proxy turned on correctly. You also have to convert all the strips as Blender can't play mixed proxy/not proxy media. 

To do this, in the timeline of the sequence editor press N. Scroll down a bit and tick the box labelled Proxy/Timecode. Change the options to suit your needs.



Then, click on Strip > Rebuild Proxy and Timecode indicies.



Finally, to have playback use these proxies, in the playback window press N, and then change the Proxy render size to make the size of your proxies.